Bias adjustment for spotting rifles



Jan. 11, 1966 A. J. GRANDY BIAS ADJUSTMENT FOR SPOTTING RIFLES 2 Sheets-Sheet 1 Filed Nov. 18, 1963 /'g, PT U @GG .QQQ- l INVENTOR.

ANDREW J. GRANDY BY M J j 1 M!- EM )L 1.9 ATTORNEYS.

Jan. 11, 1966 A. J. GRANDY BIAS ADJUSTMENT FOR SPOTTING RIFLES 2 Sheets-Sheet 2 Filed Nov. 18, 1963 INVENTOR ANDREW J. GRANDY BY fi t M} LaJ/v Z E J M M 1PM ATTORNEYS.

spect to the aXis of the large gun.

United States Patent BIAS ADJUSTMENT FOR SPOTTING RIFLES Andrew J. Grandy, North Hills, Pa., assignor to the United States of America as represented by the Secretary of the Army Filed Nov. 18, 1963, Ser. No. 324,590 9 Claims. (Cl. 89--41) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a mechanism by means of which a spotting rifle may have its axis adjusted with re- An object is to provide such an adjustment device that is of few parts, is simple 'yet rugged in construction and may be quickly and easily adjusted, and gives'equal graduations for equal increments of distance in either elevation or azimuth.

During the many years that spotting rifles have been used mounted on a larger gun there has been a need to have the spotter trajectory approach as closely as possible to that 'of the larger weapon under different propellants and widely different temperatures. Heretofore elaborate time consuming adjustments have been necessary in training and practice.

According to this invention an adjustment mechanism of few parts has been provided enabling such adjustments to be quickly and easily made for a straight line characteristic in as small as changes as 1 mil or fractions thereof. Specifically toothed gears, one for elevation changes and the other for deflection or azimuth changes have their teeth of progressively different depths so that a supporting guide ring engages each such gear at opposite positions, which are 90 from the other gear. The

gears are so constructed that the depth of teeth on one side rear end portions of the bracket supporting the spotting rifle.

FIG. 4 is a longitudinal section through another embodiment of this invention in which there is no need to have the expense of small tolerances.

FIG. 5 shOWs the elevation guide ring and the front view of the azimuth adjustment ring.

As shown'in FIG. 1 a portion of the barrel of 'a recoilless rifle is provided with bracket 12 shrunk around 'barrel 10 and supporting a spotting rifle barrel 11. The bracket 12 has an enlarged forward portion 13 around the spotting rifle barrel 11.

shown also in FIG. 3, provides a pivot about which the barrel 11 is adjustable.

An enlarged rear portion 14 Referring to FIGS. 2 and 3 an elevation ring gear 15 slidably secured to the barrel 11 to be angularly adjustable thereon. Surrounding the gear 15 is a supporting guide ring 16. Slidably adjustable around guide ring 16 is an azimuth ring gear 17 whose opposite horizontal teeth are engaged by horizontal grooves on the inner surface of bracket portion 13. A circular seal portion 18 .keeps dust out of gears 15 and 17. A retainer ring 19 is threaded within portion 13 for pressing ring gears 15 and 17 against the supporting guidering 16 and this latter 'fi'nga'gain'st a shoulder 20 in portion 13. -A locking pin 21 of the cotter type holds ring 19 against becoming loose. At the portion 14 a shoulder 22 serves as an abutment ree for spring washer 23 pressing against the ball seat segment ring 24 which is contiguous with a shock absorbing ring 25. A retainer ring 26 is threaded within portion 14. A locking pin 27 holds ring 26 against becoming loose. Ball portions not shown are secured to the exterior of barrel 11 and these ball portions are socketed in segments 24 to permit pivotal movement of barrel 11 as it is adjusted in either or both azimuth and elevation to reduce mismatch with the larger barrel 10. The ball segments secured to the barrel 11 and the seat segments 24 are each arranged so that the segments of one may pass between the segments of the other and then relatively rotated to bear against each other. No claim is made to this ball seat construction broadly.

Referring to the ring gear 15 in FIG. 2, the tooth 15a at the 9 oclockposition has the least height or depth and from this tooth the teeth are successively of equal and increasing increments of radial height to the tooth 15b at the 3 oclock position in both clockwise and counterclockwise movements from toot-h 15a. In this way the sum of the radial heights of each opposite pair ofteeth is constant. Preferably the increment of change in height of these teeth is such in moving to an adjacent tooth or number of teeth that a change of 1 mil or a number of mils result-s corresponding to the number of teeth passed over. The supporting and guide ring 16 is angularly fixed in the position illustrated with respect to the barrels 10 and 11. Were elevation gear ring 15 to be moved 2 teeth in a counterclockwise rotation of gear 15 then the elevation of spotting rifle barrel is increased by 2 mils. The teeth on azimuth gear -17 change in a similar manner and equal increments of height change from the tooth 17a of minimum height to tooth 17b of maximum height. Opposite teeth of gear 17 are received in opposite grooves on the inside of enlarged portion 13 and these grooves are angularly fixed with respect to barrels 10 and 11. Were gear 17 to be moved 1 tooth in a clockwise direction from the position illustrated in FIG. 2. the muzzle of the spotting rifle is moved 1 mil to the left in FIG. 2 which is equivalent to 1 mil to the right of the gunner facing toward the muzzle from a position in rear of it.

An advantage of this construction is the saving of time and simplicity in construction. Both gears 15 and 17 are removable together for simultaneous adjustment. After removal of retainer ring 19 and seal 18 to avoid possibility of not knowing where the elevation and azimuth rings were formerly located or where they are to be moved, they may appropriately be marked to avoid error in making the change. The clearance between teeth and their receiving grooves in FIG. 2 is about .001 of an inch or just enough to provide a sliding fit in the grooves. As shown each of gears 15 and 17 has 20 teeth. They may have a different number of teeth and the equal increment in tooth height or depth need not always be an amount to produce 1 mil in angular change although that amount is preferred.

Another embodiment of this invention is shown in FIG. 4 in which the elevation and azimuth gears may be locked solidly to 'be free of all lost motion without prohibitive expense in cost of production for the small tolerances desired in FIGS. 1 to 3.

In this embodiment of FIGS. 4 and 5 the spotting rifle barrel 11 extends through bracket as before and now numbered differently, but has an adjustable forward bracket portion 29 of different shape from that shown in the preceding figures of the drawing. The elevation ring 30 is angularly adjustable on the barrel 11 but its teeth are shown at an angle of approximately 45. A supporting guide ring 31 instead of a groove to engage only the outer surface of a tooth, has vertical projections at the 12"oc'l'ock and 6 oclock positions as before' but such projections engage the inclined bottom surface between teeth. In both embodiments the supporting guide ring may be said to engage the elevation ring gear and the increments of tooth depth affect the setting of the barrel. In FIGS. 2 and 3 the supporting guide ring engaged the top and bottom of opposite teeth whereas in FIG. 4 the guide ring engaged the inclined surface at the base of the teeth, but in both embodiments the adjustment of the barrel 11 may be said to depend on tooth depth. Also both embodiments may be regarded as having projection and recess type connections between the elevation ring and a supporting guide ring for that elevation ring. In both embodiments the azimuth gear or ring has a projection and recess type connection between it and a cooperating supporting guide ring. In both embodiments the guide rings for the elevation and azimuth gears engage opposite teeth at the 6 and 12 oclock and at the 3 and 9 oclock positions respectively for moving the spotting barrel with respect to a forward bracket portion about a pivot center of the spherical or ball segments. In the embodiment of FIGS. 4 and the guide ring 31 for the elevation gear has limited play in a horizontal direction to allow adjustment of the azimuth gear 32 and its guide ring 33 but the ring 31 has no more play in a vertical direction than enough to insert it in position in the forward bracket portion 29. In the same way the guide ring 33 for the azimuth gear has about the same limited play in a vertical but not in a horizontal direction. Both embodiments have a retaining ring for holding each gear in position. In FIG. 4 there are two retaining rings 34 and 35 while in FIG. 3 only one is needed.

Advantages of the construction of FIG. 3 over that in FIG. 4 is that both azimuth and elevation gears may be removed substantially simultaneously. On the other hand in FIG. 4 it is necessary to move only one gear when only one of them needs adjustment. An important advantage in the FIG. 4 embodiment over that in FIG. 3 is the fact that the inclined teeth make it possible for all lost motion to be eliminated and each gear to be locked solidly in adjusted position whereby the expense of obtaining small tolerances can be eliminated. This is made possible by each guide ring being able to engage an inclined surface at a position where there is a tight fit depending on the retaining rings 34 and 35 being tightened by their peripheral threads shown. Two springs 36 and 37 abut one another and are of use in assisting in the removal of gears 30 and 32 after removal of the retaining rings 34 and 35.

I claim:

1. The combination with a large gun barrel, a spotting rifie barrel displaced from and secured to said large gun barrel, and a bracket by means of which said spotting rifie barrel is fixed to said large gun barrel, of the improvement by means of which the spotting rifle barrel may be adjusted in at least one of elevation and azimuth quickly and easily with respect to the large gun barrel, said improvement including a toothed ring angularly slidably fitting around said spotting rifie barrel, a guide ring surrounding said tooth ring and supported thereon by a projection and recess type connection at diametrically opposite portions of said tooth ring, the teeth depth being of a size and spacing to provide adjustment of said spotting rifie barrel on relative rotation of said toothed ring in one direction and on such rotation in an opposite direction to effect an opposite angular adjustment of said spotting rifle barrel, the change in depth of successive teeth determining the change in angular displacement of the spotting rifle from its previous position.

2. A combination according to claim 1 in which a bracket encloses said tooth ring, a guide ring surrounding said toothed ring, and a threaded retainer is in threaded engagement in said housing for holding said guide and toothed rings in the housing.

3. A combination according to claim 2 in which a second toothed ring is provided for making adjustment of said spotting rifle barrel at 90 to the plane in which the adjustments made by the first mentioned toothed ring were eflFected.

4. A combination according to claim 3 in which said toothed rings have teeth inclined to one another whereby said guide ring for at least one toothed ring could have a snug fit in its inclined teeth, thereby eliminating the need for close manufacturing tolerances.

5. A combination according to claim 4 in which the two toothed rings are shaped as bevel gears and there is a guide ring around each toothed ring and a spring device is placed between each of said toothed rings with inclined teeth and each of said toothed rings is secured around the spotting rifle barrel.

6. A cylindrical body, a housing pivoted to said body, and means for adjusting said body with respect to the axis of said housing in planes normal to each other, said means including rings on said body and having inclined teeth, a guide ring around each of said toothed rings, said toothed rings each having teeth of successively and equally varying depth for about in one direction and of successively varying direction in an opposite direction, a retaining ring for engaging said housing and said inclined toothed ring, a guide ring between each toothed ring and its retaining ring, there being an inclined projection and recess type connection between each guide ring and the inclined toothed ring with which it engages, and spring means surrounding said cylindrical'body and between said toothed rings with inclined teeth to assist in the adjustment of either ring with inclined teeth.

7. In a combination of a large gun barrel with a spotting rifle barrel displaced from and secured to said large gun by a bracket, the combination therewith of the improvement enabling the spotting rifie barrel to be quickly and easily adjusted in either or both elevation and azimuth with respect to the larger gun barrel, said improvement including a toothed elevation ring snugly fitting around the spotting rifle barrel for angular adjustment thereon, a guide ring surrounding said elevation ring and having a groove fitted around and supported on the periphery of vertically opposite teeth of said elevation ring, the upper teeth on said elevation ring being successively larger in height in one direction by a definite amount and successively smaller in height in an opposite direction by the same amount from a mid position, the teeth on the lower side of said elevation ring being successively different in height by the same definite amount so that as said elevation ring is turned in one direction the height of the teeth increase by the same amount the opposite teeth decrease in height, a toothed azimuth ring snugly rotatably mounted on said guide ring, an end portion of said bracket having horizontal grooves engaging opposite teeth of said azimuth ring, said azimuth ring having teeth of successively increasing heights in one direction from a horizontal mid position and of decreasing height in an opposite direction with the sum of the diametrically opposite teeth equal in height to make the diameter of each pair of opposite teeth of the azimuth ring of equal value and the diameter of each pair of opposite teeth of the elevation ring equal to the diameter of every other pair of teeth on the same ring, whereby on removal of either of the elevation and azimuth rings from its guide grooves and angular displacement before its return to its guide, said spotting rifle barrel may be adjusted in either elevation or in azimuth with respect to the larger gun.

8. A combination according to claim 7 in which a seal ring is provided contiguous said elevation and azimuth rings on their front side to keep out dust and dirt, and a retainer threaded into a front end of the spotting rifle supporting bracket for holding said seal, rings and guide in place in said bracket, said spotting rifle barrel being pivotally adjustable about a ball seat held in a rear portion of said spotting rifle bracket, and said guide ring radially outside said elevation ring being secured against angular displacement with respect to said spotting rifle barrel when it is in its adjusted position.

9. A cylindrical member provided with a support and means for angularly adjusting said member in either or both of planes through said member normal to each other, and about a pivotal center longitudinally spaced from said means, said means including toothed rings, one within the other, most of the teeth on each ring being of gradually changing height with respect to adjacent teeth, and a guide ring with respect to which each of the adjacent teeth, and a guide ring with respect to which each 6 ring having diametrically opposite grooves in which opposite teeth on said inner ring are adjustably received, said outer toothed ring being rotatably adjustable on said guide ring, and said support for said cylindrical member being provided with opposite inside grooves for receiving opposite teeth from said outer ring.

No references cited.

BENJAMIN A. BORCHELT, Primary Examiner.

of the adjacent rings is angularly adjustable, said guide 10 FRED Q MATTERN, JR Examinen 

1. THE COMBINATION WITH A LARGE GUN BARREL, A SPOTTING RIFLE BARREL DISPLACED FROM SAID SECURED TO SAID LARGE GUN BARREL, AND A BRACKET BY MEANS OF WHICH SAID SPOTTING RIFLE BARREL IS FIXED TO SAID LARGE GUN BARREL, OF THE IMPROVMENT BY MEANS OF WHICH THE SPOTTING RIFLE BARREL MAY BE ADJUSTED IN AT LEAST ONE OF ELEVATION AND AZIMUTH QUICKLY AND EASILY WITH RESPECT TO THE LARGE GUN BARREL, SAID INPROVEMENT INCLUDING A TOOTHED RING ANGULARLY SLIDABLY FITTING AROUND SAID SPOTTING RIFLE BARREL, A GUIDE RING SURROUNDING SAID TOOTH RING AND SUPPORTED THEREON BY A PROJECTION AND RECESS TYPE CONNECTION AT DIAMETRICALLY OPPOSITE PORTIONS OF SAID TOOTH RING, THE TEETH DEPTH BEING OF A SIZE AND SPACING TO PROVIDE ADJUSTMENTS OF SAID SPOTTING RIFLE BARREL ON RELATIVE ROTATION OF SAID TOOTHED RING IN ONE DIRECTION AND ON SUCH ROTATION IN AN OPPOSITE DIRECTION TO EFFECT AN OPPOSITE ANGULAR ADJUSTMENTS OF SAID SPOTTING RIFLE BARREL, THE CHANGE IN DEPTH OF SUCCESSIVE TEETH DETERMINING THE CHANGE IN ANGULAR DISPLACEMENT OF THE SPOTTING RIFLE FROM ITS PREVIOUS POSITION. 